Resilient rubber-like suction cups of vinyl, urethane, etc. are in prevalent use in supporting various objects, often ornaments or trinkets from surfaces of glass, tile, or other smooth non-porous surfaces. By reason of the resilient nature of such suction cup, the periphery thereof is not able to establish a vacuum-tight seal over imperfections or irregularities in the surface to which applied and hence such suction cups will fall off from time to time even from seemingly perfectly flat surfaces of glass.
In my copending application, Ser. No. 061,949, filed July 13, 1979, and entitled "Coating of Optical Lens for Blocking Purposes", a motor driven resilient suction cup having a vacuum releasing source is applied on the concave side of an optical lens for spin coating the convex side of the lens for blocking purposes. A low melting point blocking alloy is cast against the coating on the convex side thereof for mounting of the blocked lens in a grinding and polishing machine for grinding and polishing the concave side. In the method disclosed in said copending application, the downwardly facing convex side of the lens while held by the suction cup is dipped in the coating material in a can and upwardly withdrawn therefrom whereupon spinning of the lens about its vertical axis spreads out the coating material by centrifugal force as a uniform thickness film covering the convex side of the lens. Occasionally, if there is foreign matter on the concave side of the lens, or if there are imperfections on the concave side, such as to prevent the formation of a vacuum-tight seal between the lens and suction cup, the spinning lens may be dislodged from the suction cup either damaging the lens or throwing it off into the can of coating material with the bother of removing it from the can and cleaning off the coating material from both sides and peripheral edge.
Furthermore, some lenses are provided with raised characters, i.e., numbers and letters on the concave side which may make impossible the obtaining of a vacuum-tight seal when such suction cup is applied against the concave side of the lens.